Soft Magnetic Alloy Coating via Controlled Oxidation
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Solution Overview
Problem
Existing methods for forming insulating films on soft magnetic alloy ribbons result in coatings with low electrical resistivity due to the presence of FeO or Fe3O4, which limits the thickness reduction of these films while maintaining insulation properties, hindering the increase of the motor core's space factor and energy efficiency.
Innovation Solution
A method involving heating a soft magnetic alloy substrate in an atmosphere with water vapor and inert gas, specifically with an oxygen partial pressure between 0 to 1.5 kPa, to form a single-phase α-Fe2O3 film with high electrical resistivity, preventing the formation of low resistivity iron oxide phases like Fe3O4 and FeO.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the thickness of the insulating film is decreased to increase the space factor, then the motor size is reduced, but the insulation property deteriorates due to low electrical resistivity of the coating
Solution Approach 1:
The patent changes the chemical composition parameter of the coating by controlling the oxidation process to form a single-phase α-Fe2O3 film instead of mixed-phase coatings. This parameter change (from mixed FeO/Fe3O4/α-Fe2O3 to pure α-Fe2O3) dramatically increases electrical resistivity, enabling thin film thickness while maintaining insulation properties.
Solution Approach 2:
The patent utilizes phase transition during heat treatment to transform the coating from a mixed-phase structure (containing low-resistivity FeO and Fe3O4) to a single-phase α-Fe2O3 structure. By controlling the heating atmosphere (oxygen partial pressure of 0.003-1.5 kPa) and temperature (200-450°C), the phase composition is controlled to achieve high electrical resistivity even at reduced film thickness.
2Ease of manufacture
If conventional heat treatment methods are used to form the coating, then the coating formation process is simple, but the electrical resistivity remains low due to presence of FeO and Fe3O4
Solution Approach 1:
The patent modifies the atmospheric parameter (oxygen partial pressure) during heat treatment to control the oxidation process. By maintaining oxygen partial pressure between 0.003-1.5 kPa, the coating is transformed into single-phase α-Fe2O3 with high electrical resistivity, while keeping the process simple and compatible with existing heat treatment equipment.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method enables the formation of a soft magnetic member with a high electrical resistivity coating, allowing for a reduced motor size and improved energy efficiency by increasing the motor core's space factor without compromising insulation properties.
Implementation Method 1
heating a soft magnetic alloy substrate in an atmosphere containing water vapor and inert gas to form a coating on the soft magnetic alloy substrate
Implementation Method 2
The soft magnetic member manufactured by the manufacturing method of the present disclosure has the coating formed of the α-Fe2O3 single phase having the high electrical resistivity
Data Source
AI summary
There is provided a method for manufacturing a soft magnetic member where a coating formed of an α-Fe2O3 single phase having a high electrical resistivity is formed on a soft magnetic alloy substrate. A soft magnetic alloy substrate is heated in an atmosphere containing water vapor and inert gas to form a coating on the soft magnetic alloy substrate. The atmosphere has an oxygen partial pressure in a range of 0 to 1.5 kPa. A soft magnetic member including the soft magnetic alloy substrate and the coating formed on its surface can be obtained.